Stratospheric aerosol retrieval with optical spectrograph and infrared imaging system limb scatter measurements

Abstract

An algorithm for the retrieval of global stratospheric aerosol profiles is presented using the optical spectrograph and infrared imaging system limb scatter measurements as an example data set. The retrieval utilizes a one‐dimensional version of the MART nonlinear relaxation inversion suitable for limb scatter. A height profile of the particle size distribution must be assumed in order to retrieve the aerosol number density. An altitude normalized wavelength ratio measurement vector is employed to minimize effects of upwelling radiation from ground albedo and uncertainties in the neutral density profile. Using a method of numerical perturbation, a formal error analysis is performed that shows that the dominant error term is the measurement noise. Comparison with stratospheric aerosol and gas experiment (SAGE) II and SAGE III coincident measurements of extinction shows agreement with the limb scatter retrievals to within 15% throughout the lower stratosphere for an appropriate choice of particle size distribution. The relatively high sampling resolution of the limb scatter technique makes this data set of interest for studying the dynamics of the stratosphere, stratosphere/troposphere exchange, and for extending the long history of the aerosol data record from the SAGE series of occultation measurements.